A metering machine generally comprises a frame receiving a hopper that serves to receive, in loose form, the food for canning, a duct that opens out in the hopper in the vicinity of a bottom thereof and that receives a portion of a transfer screw or “auger” extending along the bottom of the hopper, and a metering cylinder that slidably receives a suction and delivery piston. For reasons of compactness, the metering cylinder is disposed horizontally under the hopper. The bottom of the hopper and the duct are inclined relative to the horizontal so that the cylinder and the duct form an acute angle between them and are connected together via a plug valve. That type of machine is not adapted to all kinds of food because some foods, in particular grated carrot and sticky foods tend to form a blockage in the vicinity of the plug valve. If the blockage is not detected in time, and if the transfer screw is not stopped, the force opposing the movement of the food increases due to the blockage and increases the mechanical stresses to which the transfer screw and the drive members for driving said screw are subjected. That might damage one or more components of the machine.
The technological background to the invention can be supplemented by citing Document U.S. Pat. No. 4,399,932 which describes a volumetric dispenser with a valve having two valve members offset angularly on a common rotary shaft, and Document U.S. Pat. No. 5,088,517 which describes an injector for injecting a flowable additive into a stream of liquid.